Resuscitation from hemorrhagic shock: Fluid selection and infusion strategy drives unmeasured ion genesis

BACKGROUND: This study compares unmeasured ion generation by different resuscitation fluids and strategies for hemorrhagic shock (HS). METHODS: A rectus crush injury and 40% hemorrhage initiated controlled HS in 24 minipigs. Pigs (n = 8/gp) were untreated (NON) or bolused (10 cc/kg bw) with HBOC-201 (HBOC), or 6% Hetastarch (HEX) after 20 minutes of HS. Additional boluses occurred for hypotension (mean arterial pressure [MAP] <60 mm Hg) or tachycardia (heart rate [HR] >baseline) for 4 hours; other therapy was withheld, simulating delayed evacuation. Hemodynamics, acid-base parameters, and strong ion difference (SID) and strong ion gap (SIG), were assessed. Data are means ± SD or percent; significance for p < 0.05. RESULTS: Initial MAP was similar (p > 0.05) as was ultimate survival (p > 0.05). By 30 minutes, MAP was higher with HBOC (63 ± 8; p = 0.01) versus HEX (37 ± 5) or NON (35 ± 4). HBOC required less fluid than HEX (515 ± 58 versus 830 ± 45 mL, p = 0.019). Lactate was similar between groups (p > 0.05). pH was highest in HBOC by 180 minutes (p < 0.05). SID was constant in NON, decreased in HEX, but increased in HBOC (p < 0.05 by 60 minutes). SIG remained unchanged in NON and HEX, but declined in HBOC (p < 0.05 by 30 minutes). CONCLUSIONS: HBOC resuscitation required the least fluid. Unmeasured anions were prevalent in HEX and NON (+ SIG), whereas HBOC liberated unmeasured cations (- SIG); differences were inapparent when only evaluating pH. Only HBOC increased the SID, electrochemically promoting alkalosis. Resuscitation fluid differences may aid care in high lactate conditions where an induced counterbalancing metabolic alkalosis may be beneficial.